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bbd8a0d3a3
dev_queue_xmit enqueue's a skb and calls qdisc_run which
dequeue's the skb and xmits it. In most cases, the skb that
is enqueue'd is the same one that is dequeue'd (unless the
queue gets stopped or multiple cpu's write to the same queue
and ends in a race with qdisc_run). For default qdiscs, we
can remove the redundant enqueue/dequeue and simply xmit the
skb since the default qdisc is work-conserving.
The patch uses a new flag - TCQ_F_CAN_BYPASS to identify the
default fast queue. The controversial part of the patch is
incrementing qlen when a skb is requeued - this is to avoid
checks like the second line below:
+ } else if ((q->flags & TCQ_F_CAN_BYPASS) && !qdisc_qlen(q) &&
>> !q->gso_skb &&
+ !test_and_set_bit(__QDISC_STATE_RUNNING, &q->state)) {
Results of a 2 hour testing for multiple netperf sessions (1,
2, 4, 8, 12 sessions on a 4 cpu system-X). The BW numbers are
aggregate Mb/s across iterations tested with this version on
System-X boxes with Chelsio 10gbps cards:
----------------------------------
Size | ORG BW NEW BW |
----------------------------------
128K | 156964 159381 |
256K | 158650 162042 |
----------------------------------
Changes from ver1:
1. Move sch_direct_xmit declaration from sch_generic.h to
pkt_sched.h
2. Update qdisc basic statistics for direct xmit path.
3. Set qlen to zero in qdisc_reset.
4. Changed some function names to more meaningful ones.
Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
116 lines
3.3 KiB
C
116 lines
3.3 KiB
C
#ifndef __NET_PKT_SCHED_H
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#define __NET_PKT_SCHED_H
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#include <linux/jiffies.h>
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#include <linux/ktime.h>
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#include <net/sch_generic.h>
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struct qdisc_walker
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{
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int stop;
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int skip;
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int count;
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int (*fn)(struct Qdisc *, unsigned long cl, struct qdisc_walker *);
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};
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#define QDISC_ALIGNTO 32
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#define QDISC_ALIGN(len) (((len) + QDISC_ALIGNTO-1) & ~(QDISC_ALIGNTO-1))
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static inline void *qdisc_priv(struct Qdisc *q)
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{
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return (char *) q + QDISC_ALIGN(sizeof(struct Qdisc));
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}
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/*
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Timer resolution MUST BE < 10% of min_schedulable_packet_size/bandwidth
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Normal IP packet size ~ 512byte, hence:
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0.5Kbyte/1Mbyte/sec = 0.5msec, so that we need 50usec timer for
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10Mbit ethernet.
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10msec resolution -> <50Kbit/sec.
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The result: [34]86 is not good choice for QoS router :-(
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The things are not so bad, because we may use artifical
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clock evaluated by integration of network data flow
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in the most critical places.
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*/
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typedef u64 psched_time_t;
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typedef long psched_tdiff_t;
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/* Avoid doing 64 bit divide */
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#define PSCHED_SHIFT 6
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#define PSCHED_TICKS2NS(x) ((s64)(x) << PSCHED_SHIFT)
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#define PSCHED_NS2TICKS(x) ((x) >> PSCHED_SHIFT)
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#define PSCHED_TICKS_PER_SEC PSCHED_NS2TICKS(NSEC_PER_SEC)
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#define PSCHED_PASTPERFECT 0
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static inline psched_time_t psched_get_time(void)
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{
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return PSCHED_NS2TICKS(ktime_to_ns(ktime_get()));
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}
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static inline psched_tdiff_t
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psched_tdiff_bounded(psched_time_t tv1, psched_time_t tv2, psched_time_t bound)
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{
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return min(tv1 - tv2, bound);
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}
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struct qdisc_watchdog {
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struct hrtimer timer;
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struct Qdisc *qdisc;
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};
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extern void qdisc_watchdog_init(struct qdisc_watchdog *wd, struct Qdisc *qdisc);
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extern void qdisc_watchdog_schedule(struct qdisc_watchdog *wd,
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psched_time_t expires);
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extern void qdisc_watchdog_cancel(struct qdisc_watchdog *wd);
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extern struct Qdisc_ops pfifo_qdisc_ops;
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extern struct Qdisc_ops bfifo_qdisc_ops;
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extern int fifo_set_limit(struct Qdisc *q, unsigned int limit);
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extern struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
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unsigned int limit);
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extern int register_qdisc(struct Qdisc_ops *qops);
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extern int unregister_qdisc(struct Qdisc_ops *qops);
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extern void qdisc_list_del(struct Qdisc *q);
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extern struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle);
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extern struct Qdisc *qdisc_lookup_class(struct net_device *dev, u32 handle);
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extern struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r,
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struct nlattr *tab);
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extern void qdisc_put_rtab(struct qdisc_rate_table *tab);
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extern void qdisc_put_stab(struct qdisc_size_table *tab);
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extern void qdisc_warn_nonwc(char *txt, struct Qdisc *qdisc);
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extern int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
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struct net_device *dev, struct netdev_queue *txq,
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spinlock_t *root_lock);
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extern void __qdisc_run(struct Qdisc *q);
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static inline void qdisc_run(struct Qdisc *q)
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{
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if (!test_and_set_bit(__QDISC_STATE_RUNNING, &q->state))
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__qdisc_run(q);
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}
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extern int tc_classify_compat(struct sk_buff *skb, struct tcf_proto *tp,
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struct tcf_result *res);
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extern int tc_classify(struct sk_buff *skb, struct tcf_proto *tp,
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struct tcf_result *res);
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/* Calculate maximal size of packet seen by hard_start_xmit
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routine of this device.
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*/
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static inline unsigned psched_mtu(const struct net_device *dev)
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{
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return dev->mtu + dev->hard_header_len;
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}
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#endif
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